Audio signal processing becomes more and more important. In particular, spatial sound recording is employed in a plurality of applications. Spatial sound recording aims at capturing a sound field with the help of multiple microphones such that at the reproduction side, a listener perceives the sound image as it was at the recording location.
Standard approaches for spatial sound recording usually involve spaced, omnidirectional microphones (e.g., AB stereophony) coincident directional microphones (e.g., in intensity stereophony), or more sophisticated microphones, such as a B-format microphone, e.g., in Ambisonics, see, for example,
[1] Michael A. Gerzon. Ambisonics in multichannel broadcasting and video. J. Audio Eng. Soc, 33(11):859-871, 1985.
A spatial microphone, for example directional microphones, microphone arrays, etc, is capable of recording spatial sound. The term “spatial microphone” refers to any apparatus for the directionally selective acquisition of spatial sound (e.g. directional microphones, microphone arrays, etc.).
For sound reproduction, existing non-parametric approaches derive desired audio playback signals directly from recorded microphone signals. A major disadvantage of these approaches is, that the spatial image recorded is relative to the spatial microphone used.
In many applications, it is not possible or feasible to place a spatial microphone in the desired position, which, for example, may be a position close to the one or more sound sources. In this case, it would be more beneficial to place multiple spatial microphones further away from the active sound sources and still be able to capture the sound scene as desired.
Some applications employ two or more real spatial microphones. It should be noted, that the term “real spatial microphone” refers to the desired microphone type or microphone combination (e.g. a directional microphone, a pair of directional microphones as used in common stereo microphones, but also a microphone array), which physically exists.
For each real spatial microphone, the Direction Of Arrival (DOA) can be estimated in the time-frequency domain. Using the information gathered by the real spatial microphones, together with the knowledge of their relative position, it may be possible to compute the output signals of a spatial microphone virtually placed at an arbitrary position (at will) in the environment. This spatial microphone is referred to as “virtual spatial microphone” in the following.
In such applications, the position and orientation of the one or more virtual microphones needs to be input manually. However, it would be appreciated if an optimal position and/or orientation of the one or more virtual microphones would be determined automatically.
It would be advantageous, if an apparatus and method would be available to determine, where to place a virtual microphone, where to place a physical microphone or to determine an optimal listening position. Moreover, it would be advantageous, how to place a microphone in an optimal orientation. The terms “microphone positioning” and “positioning information” relate to how to determine an suitable position of a microphone or a listener as well as how to determine an suitable orientation of a microphone or a listener.